Enhancing the immune system has become a widespread concern in society. The use of vitamin and mineral supplements may be increasing especially during winter months to against respiratory tract infections risk. A recent review, published in the British Medical Journal (BMJ), which claimed that the use of vitamin D fortification can reduce the risk of acute respiratory infections, has brought the issue onto the spotlight once again.

Previous studies on the effect of vitamin D fortification on acute respiratory tract infections in randomly selected samples and a control group yielded quite different results. This meta-analysis published in BMJ assessed the results of randomized, double-blind, placebo-controlled studies that examined valid indications of acute respiratory problems and the relationship between vitamin D fortification and acute respiratory tract infections. It compiled the results of 24 studies based on the above criteria.

The results show that vitamin D fortification has reduced the risk of acute respiratory tract infection. In addition, vitamin D supplement use daily or weekly was shown to be more effective than a single, high dose of vitamin D in a bolus application. It was also reported that individuals with low levels of 25-hydroxyvitamin D so who had vitamin D deficiency benefit more from fortification.

What’s the relation between acute respiratory tract infections and Vitamin D?

Low serum 25-hydroxyvitamin D is a basic indicator of vitamin D deficiency. Observational studies have shown that individuals with low serum 25-hydroxyvitamin D levels are more sensitive to acute respiratory tract infections. It has been reported that 25-hydroxyvitamin D supports induction of antimicrobial peptides in response to both viral and bacterial stimuli, suggesting a potential mechanism by which vitamin D inducible protection against respiratory pathogens might be mediated.

What do the results of the meta-analysis say?

Daily, weekly, or bolus vitamin D fortification can reduce the risk of acute respiratory tract infections, especially in individuals with vitamin D deficiency. Therefore, populations in which vitamin D deficiency is common, foods fortified with vitamin D can be beneficial.

Recommendations of Health and Nutrition Authorities

Scientific Advisory Committee on Nutrition in U.K. 2016 report, recommends that individuals aged 5 and over should consider to use vitamin D supplement (10 micrograms per day) from October to March if producing vitamin D from sun exposure is not adequate. People with very little or no sunshine exposure are advised to take a daily supplement containing 10 micrograms of vitamin D throughout the year. Some countries, including the U.S. and Finland have vitamin D fortification policies in place, whereas others, including the U.K. have voluntary fortification. The British Nutrition Foundation (BNF) also notes that the fortification of nutrients with vitamin D may be considered as a public health policy option in societies where deficiency is widespread, particularly in regard to bone health.

References:
1. https://www.nutrition.org.uk/nutritioninthenews/headlines/vitamin-d-for-the-common-cold.html
2. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
3. https://www.gov.uk/government/publications/sacn-vitamin-d-and-health-report